In general, the compressor in a refrigerating system compresses a working fluid passed through an evaporator in a refrigerator or an air conditioner, to supply refrigerant to a condenser. A system of a related art reciprocating type compressor will be explained with reference to FIGS. 1-3B. FIG. 1 illustrates an overall system of a related art reciprocating type compressor in a refrigerating system, schematically.
Referring to FIG. 1, the related art reciprocating type compressor is placed in a space enclosed by a lower shell 2 and an upper shell 1. The compressor is provided with a motor part for generating a rotating force as the motor part has a current applied thereto, a compression part for compressing the working fluid by the rotating force from the motor part, and an oil supply part for supplying refrigerant oil to reduce friction in a mechanical part and cool down the heated mechanical part. The motor part is provided with a stator 21 for receiving a current to generate an electromagnetic force, and a rotor 22 for generating a rotating force from the electromagnetic force of the stator. The compression part is provided with a connecting rod 31 for converting a rotating movement into a linear reciprocating movement, and a piston 32 in a cylinder block for compressing the working fluid by the connecting rod. The oil supply part is provided with a crankshaft 110 and an oil supply device 120, wherein the connecting rod 31 has one end pin coupled to an eccentric part 111 on a top of the crankshaft, and the other end pin coupled to the piston 32. Accordingly, the connecting rod 31 converts the rotating movement of the crankshaft to a linear movement of the piston.
There is an oil plate (not shown) at a lower part of the lower shell filled with refrigerant oil, with a lower end of the oil supply device 120 submerged in the refrigerant oil. There is a hermetic terminal 11 and a cluster 12 at one side of the lower shell 2 for connecting the stator 21 to an external power. The cluster 12 has a plurality of lead wires 13 branched from the stator 21 fixed by terminals (not shown), which are connected with a plurality of pins passed through the hermetic terminal 11.
The oil supply part will be explained with reference to FIGS. 2-3B. FIG. 2 illustrates a front view of the oil supply part for the compressor in a refrigerating system, FIG. 3A illustrates a section of a piece press fit in a lower end of the crankshaft in FIG. 2, and FIG. 3B illustrates a front view of the oil supply device in FIG. 2, an insert member fitted in the piece.
The oil supply part 100 is provided with a crankshaft 110 and an oil supply part 120. The crankshaft 110 has an eccentric part 111 fitted eccentric from a shaft center, a weight balance 112 under the eccentric part 111 for prevention of vibration during rotation, and a shaft part 113 having a refrigerant oil rising passage under the weight balance 112. There is an oil hole 113b in the middle of length of the shaft part 113 in communication with an outside of the shaft part 113, and a helical oil groove 113a along an outer circumference of the shaft part 113 extended from the oil hole 113b to the eccentric part 111 on top of the crankshaft. There is a drill hole 113c in communication with the oil hole 113b, formed lengthwise eccentric from an axis of the shaft part 113.
According to this, when the crankshaft is rotated, the refrigerant oil introduced into the drill hole 113c by a centrifugal force of the oil supply device 120 flows to the oil groove 113a through the oil hole 113b, and is sprayed onto a mechanical part as the refrigerant oil reaches the eccentric part 111 through the oil groove 113a. The refrigerant oil sprayed thus lubricates the compressor, and absorbs heat generated during operation of the compressor. This sprayed refrigerant oil prevents the compressor from suffering damage caused by a high temperature and friction.
There is a gas hole 113d in one side of the drill hole 113c opened in a point of a circumference of the shaft part 113 having a greatest distance to the drill hole 113c for discharging gas formed when the refrigerant oil is moved upward and outside of the crankshaft 110 as the oil supply part is rotated.
In the meantime, the oil supply device 120 for pumping the refrigerant oil by using the centrifugal force has a cylindrical piece 131 inserted in a lower end of the shaft part 113 of the crankshaft 110, and an insert member 122 fitted in the piece 131 for forming a rising passage of the refrigerant oil.
The foregoing oil supply device 120 in the lower end of the rotating crankshaft 110 rotates together with the crankshaft, when the refrigerant oil is pumped to the drill hole 113c as the refrigerant oil flows upward through the insert member in the oil supply device 120 by the centrifugal force, and, therefrom, to the oil groove 113a through the oil hole 113b. Then, the refrigerating oil lubricates a journal bearing (not shown) as the refrigerant oil flows upward along the oil groove 113a, and, at the end, moves up to the eccentric part 111 and is sprayed onto the mechanical part in the shell 1 and 2. The refrigerant oil sprayed thus is recovered by the oil plate at a lower part.
In the meantime, in order to reduce a power consumption of a refrigerating system, currently a pole changing, or BLDC motor, operative at a low speed, as well as at a high speed, is widely used as a compressor motor. However, the oil supply device provided for a high speed operation (approx. 3600 rpm) can not supply the refrigerant oil smoothly during a low speed operation (approx. 1800 rpm). That is, as the centrifugal force that is generated by the rotation of the oil supply device to move the refrigerant oil upward drops sharply when the compressor is operated at the low speed, the oil supply part can not supply the refrigerant oil, properly. Eventually, the compressor is involved in an excessive wear of the mechanical part, with a substantial reduction of lifetime of the compressor and an increased noise, as the compressor has a reduced performance of a heat dissipation, and reduced supply of the refrigerant oil.